I also have a Satmap Active 10 that has survived several crashes plus being left on the back of my car as I drove home and bouncing across the road in the central roundabout near Swinley.
I think it is exceptional - the only problem is cost. £300 for the unit and then map cost - I have a 1:25k 70kx70k map centered on Guildford that covers my riding on the Surrey Hills and Swinley Forest, which cost about £70 - and a 1:50k UK whcih cost £160.
The display is the OS map in 2D - which you can have orientated with north up or as 'trail' up which has your direction of movement as up. Hence you can see if you have to turn left or right and when - I find riding at 1:3K resolution best for this. You can therefore ride at full speed most of the time, unless the trail has changed...
Obviously you can upload gpx and google kml files onto it, and you can trace out a route on the unit using the joystick, whcih you can also use to edit trails if you find that part of it has moved (tree felling, etc).
You choose which trail you are going to follow (the active route) and it is highlighted in light brown. You can also set the unit to show inactive trails also, which are shown as light grey.
Therefore as you follow the route you can see all the other trails you are passing in case you wish to detour onto them - it could be a loop of singletrack for example.
I have all my routes as kml files and use Google Earth to view them all and work out which one, or combinations, I am going to follow. I have grabbed loads of routes for Surrey Hills and Swinley from the net as well.
I have to say that the display on the Garmin 305 looks prehistorically poor in comparison...
Apparently they are working on a new model - I meet a friend of the guy who started the (UK based) company the other day whilst riding - the founder is an ex fighter pilot from the UK air force.